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Pre-BDS3 Radiology > Panoramic Radiography > Flashcards

Panoramic Radiography Flashcards

1
Q

what is tomography

A

technique allowing slices of the subject to be viewed separately

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2
Q

what are the two types of tomgraphy

A

conventional = one slice
computed = multiple slices

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3
Q

how is tomography produced

A

using different phenomena - x-rays/radio waves etc.,

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4
Q

what kind of tomography does panoramic radiographs use

A

linear tomography

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5
Q

what is linear tomography

A

the way of capturing a single, flat slice by moving the x-ray source and receptor past the area of interest during the exposure

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6
Q

what is the focal trough

A

thin band where images appear adequately sharp

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7
Q

where is the focal trough thinner

A

incisor region

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8
Q

why is the incisor region thinner in the focal trough

A

it is related to the speed of rotation at this point

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9
Q

what does orthogonal view mean

A

x-ray beam is more 90 degrees to the teeth

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10
Q

what are the advantages of an orthogonal view

A

reduces overlap of teeth to aid approximal caries assessment
improves angulation to more accurately represent interdental periodontal bone levels

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11
Q

what are the disadvantages of an orthogonal view

A

distorts rest of skeleton to varying degrees
narrower field of view so miss condyles

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12
Q

when is an orthogonal view appropriate

A

for cases requiring only caries or periodontal bone loss

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13
Q

in what direction relative to the focal trough do structures appear magnified

A

lingual to the focal trough

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14
Q

in what direction relative to the focal trough do structures appear smaller

A

buccal to the focal trough

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15
Q

if a subject is within the focal trough how much is it magnified by

A

about 25%

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16
Q

why are structures within the focal trough not distorted

A

the degree of horizontal magnification matches that vertically

17
Q

how does distortion affect subjects buccal to the focal trough

A

appear narrower

18
Q

how does distortion affect subjects lingual to the focal trough

A

appear broader

19
Q

why do teeth get distorted if lingual or buccal to the trough

A

the beam sweeps from one side of the jaws to the other but x-ray source is always lingual to the focal trough

20
Q

why are structures positioned further away from the receptor projected further up on the image

A

due to the angulation of the beam

21
Q

what are the advantages of panoramic radiographs

A

can capture entire dentition in one image
able to image non-dental areas
lack of intra-oral holders benefits some patients

22
Q

what are the disadvantages of panoramic radiographs

A

worse clarity
longer exposure time
higher radiation dose per image

23
Q

what are the main components of the OPT machine

A

x-ray tubehead, receptor, control panel, patient positioning

24
Q

how do you prepare the patient for an OPT

A

remove metal foreign bodies, position patient in machine, advise patient of tongue to roof of mouth, stand still, no swallowing

25
Q

what apparatus helps to position the patient

A

bite peg, light beam markers, head grabber, chin rest

26
Q

what is the correct positioning of the frankfurt plane and mid-sagittal plane

A

frankfurt - horizontal
mid-sagittal - centred in midline

27
Q

what happens if the patient is too far forward in the machine

A

incisors are buccal to focal trough and appear narrower

28
Q

what happens if the patient is too far backward in the machine

A

incisors now lingual to focal trough and appear wider

29
Q

what are the instructions to the patient during the scan

A

stay still, press tongue up against palate, not talk or swallow

30
Q

what are the appearance of movement artefacts affected by

A

direction of movement, duration of movement, speed of movement, timing of movement, structures moving

31
Q

why is no lead apron used for dental radiography

A

it is not justified as the beam is not directed at the abdomen

32
Q

what is on the quality standards checklist

A

patient preparation/instruction adequate
no patient positioning errors
correct anatomical coverage
good density and contrast

Pre-BDS3 Radiology (17 decks)

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